This invention relates to emulsions of a polar liquid in a non-polar liquid. In one aspect this invention relates to aqueous solutions-in-polydimethylsiloxane emulsions using a mixture of a silicon-free emulsifier and a silicon-containing copolymer as the emulsifying agent. In another aspect this invention relates to aqueous emulsions which are dilutable with paraffinic hydrocarbons.
Water-in-oil emulsions are well known and there exists many organic emulsifiers which are operable for their preparation and stabilization. For example, Lachampt, et al., U.S. Pat. No. 3,489,690 describes water-in-oil emulsions using certain polyoxyalkylene alcohols as the emulsifiers. The oil phase may comprise silicone oils which are soluble in the oil. When one attempts to prepare a water-in-low-viscosity polydimethylsiloxane emulsion, however, said organic emulsifiers do not provide suitably stable emulsions. This is especially noticeable when the aqueous phase contains a dissolved solute.
Aqueous lubricating compositions are taught by Pater, U.S. Pat. No. 3,234,252 which employ a siloxane-polyoxyalkylene copolymer as an additive. These compositions are said to be either solutions or water-in-oil emulsions or oil-in-water emulsions; however, no water-in-oil emulsions are indicated. Moreover, Pater's concentrated compositions are described as being dilutable with water or mixtures of water and an organic lubricant base fluid, thereby suggesting that said emulsions are oil-in-water emulsions. When one attempts to prepare water-in-low viscosity polydimethylsiloxane emulsions, using only a siloxane-polyoxyalkylene copolymer as an emulsifier, suitably stable emulsions are not obtained, although they are frequently more stable than when prepared using only organic surfactants.
We have found that stable emulsions of a polar liquid, e.g. water, in a non-polar liquid, e.g. a polydimethylsiloxane fluid can be prepared if a mixture of certain organic surfactants and certain polydiorganosiloxane-polyoxyalkylene copolymers is used as the emulsifying agent.
Mixtures of organic surfactants and siloxane-oxyalkylene copolymers have been used before. For example, a siloxane-oxyalkylene block copolymer has been used by Bailey, et al. U.S. Pat. No. 3,562,786 to lower the surface tension of an aqueous solution of an organic surfactant, however, these compositions are oil-in-water emulsions.
Water-in-oil siloxane emulsions are disclosed by Nitzsche, et al., Canadian Patent No. 742,289; however, the oil in these compositions is a siloxane-polyoxyalkylene copolymer and does not comprise a non-polar liquid such as a polydimethylsiloxane or a paraffinic hydrocarbon.